What is Diabetic Foot Infections?
Approximately 29 million people in the United States have diabetes, and about 25% of people over the age of 65 are affected by this disease. The occurrence of diabetes worldwide is expected to increase by 55% in the next 20 years, showing that this issue is only set to grow. A common complication of diabetes is a type of nerve damage called distal symmetric polyneuropathy (DSP), which affects about 75% of diabetic patients.
When DSP develops, the chances of developing ulcers (open sores) each year jump from less than 1% to over 7%. Additionally, in individuals who are diabetic, having an ulcer increases their chances of dying within three years from 13% to 28%. Diabetes can also affect the blood flow in the body, and this can open the door to infections that can range from ordinary skin infections to severe tissue death (gangrene).
Osteomyelitis, a kind of bone infection, can occur in 15% of these ulcers and 15% of those infections may result in amputation (removal of a part of the body). In fact, about 60% of patients who undergo lower limb amputation have diabetic foot ulcers as the main cause. Following an amputation, there’s a 60% chance of dying within five years. Because diabetic foot ulcers can lead to amputation and death, every effort should be made to prevent them.
Treating diabetic foot infections can be a challenge as the diminished blood flow can make it difficult for antibiotics to reach the affected area. Many people with diabetes find that a foot infection can rapidly worsen, and the process to recovery may take longer than it would for a person without diabetes.
What Causes Diabetic Foot Infections?
There are several aspects that contribute to the development of foot ulcers in individuals with diabetes. The four main factors include nerve damage (neuropathy), poor blood circulation (ischemia), nutritional issues, and infections. As it turns out, a foot that has good blood flow is less likely to develop ulcers and infections than one with poor circulation, a condition often seen in peripheral vascular disease.
In people with diabetes, this problem is made worse by neuropathy, which can disrupt the body’s natural ability to direct blood to where it’s needed most. This condition reduces blood flow to small blood vessels and redirects it around larger ones.
Nerve damage in the feet also can reduce sensations and cause a loss of sweat and oil glands. Consequently, the skin on the feet may become dry and cracked, and people may not notice when they have wounds or infections. Furthermore, high blood sugar levels can cause tendons to stiffen and shorten, which can lead to foot deformities like claw toes or hammer toes, and stiffening of the Achilles tendon. All of these problems increase pressure on the front of the foot.
It’s also important for those with diabetes to wear proper footwear. Shoes that don’t fit correctly can increase pressure on certain parts of the foot, disrupt blood flow, and make the foot more prone to infection. Diabetes can also make any existing peripheral vascular disease worse.
The types of bacteria that typically cause infections in the feet of individuals with diabetes include staphylococcus, streptococci, and pseudomonas, along with many other types of bacteria, including those that produce gas. Such infections are commonly seen in people with diabetes.
Risk Factors and Frequency for Diabetic Foot Infections
Diabetic foot infections are frequent infections among people with diabetes. These infections tend to be more common in older adults with other health conditions. Both men and women are affected by diabetic foot infections.
Death from diabetic foot infections is relatively rare, but can increase with certain conditions. Those who have a higher risk include patients with chronic bone infections, those with rapidly decaying soft-tissue infections, and those with additional health problems that weaken the immune system.
Signs and Symptoms of Diabetic Foot Infections
If someone has diabetes, it’s important to ask about certain risk factors for foot ulcers related to diabetes. These could include a previous foot ulcer, loss of feeling from nerve damage, irregular pulse strength, blood circulation problems in the legs and feet, a deformed foot, being 65 years or older, difficulty controlling blood sugar levels, organ damage from diabetes, and kidney disease. If a person is known to be at risk, they should regularly wear special shoes designed to reduce pressure on their feet. If an ulcer has already formed, it’s crucial to know what type of footwear the person is using and what treatments they’ve tried before.
As part of the check-up, the doctor should check for signs of circulation problems in the legs and feet, loss of feeling due to nerve damage, and assess the depth and severity of the ulcer.
- Previous foot ulcer
- Loss of feeling from nerve damage
- Irregular pulse strength
- Blood circulation problems in the legs and feet
- Deformed foot
- 65 years or older
- Difficulty controlling blood sugar levels
- Organ damage from diabetes
- Kidney disease
All wounds need to be carefully inspected for signs of a long-term bone infection called “chronic osteomyelitis”. If an ulcer penetrates deep into the tissue, there might be deep passages of infection. Finally, the pulse strength should be measured at each visit and a test called “Ankle-Brachial Index” performed to assess the blood flow in the legs.
Testing for Diabetic Foot Infections
Lab tests can be useful in detecting various health issues. For example, a pre-albumin test can show if you are malnourished. A blood urea nitrogen (BUN) and creatinine test checks how well your kidneys are working. A Hemoglobin A1C test measures your average blood sugar level over the past 2 to 3 months, checking if you have good control over your blood sugar levels. Additionally, if you might have a bone infection called osteomyelitis, tests such as C-reactive protein (CRP > 10) and erythrocyte sedimentation rate (ESR > 40) can be performed.
If your doctor needs to test for possible infection, it’s important to take a sample from deep within the wound, not just from the surface. That’s because most wounds have bacteria on the surface which isn’t necessarily responsible for the deep infection.
If there’s a suspicion of osteomyelitis, a bone culture is recommended. This can guide which antibiotics can be used for treatment. X-rays are also taken for all diabetic foot sores to check for foreign objects, bone infection, or gas under the skin.
Osteomyelitis can be tricky to spot on an X-ray in the early stages. It may take four to six weeks for signs to show up. So, if your doctor has a strong suspicion of the infection, an MRI can help in catching it early. If MRI is not readily available, CT scans can also be used to look for concealed abscesses.
Another useful measurement is the Transcutaneous Oxygen Measurement (TCOM). This tells the doctor how much oxygen is able to get through your skin and is vital for wound healing. An oxygen level of at least 40 mmHg is needed for a wound to heal properly. Most people with diabetes tend to have oxygen levels below this. Treatments such as hyperbaric oxygen therapy and addressing peripheral vascular disease can boost these oxygen levels. If, under hyperbaric conditions, the TCOM is more than 200 mmHg, it indicates that hyperbaric oxygen therapy is more likely to help with wound healing.
Treatment Options for Diabetic Foot Infections
When caring for wounds, the aim should be to keep the wound moist, protect against infection and treat one if it occurs, reduce pressure on the wound area, remove dead tissue and any bacterial growth or ‘biofilm’, and maximise blood flow, nutrition, and oxygen delivery to the wound. There are several ways to relieve pressure on the wound area, including removing hard skin or calluses, adding cushioning, using special shoe inserts or footwear, wearing protective boots, using full-contact casts, and lengthening the Achilles’ tendon. Hardened skin, or calluses, increase the chances of developing ulcers – removing them can reduce this pressure by 26%. The combination of lengthening the Achilles’ tendon and using a full-contact cast have the highest success rates in healing ulcers on the front of the foot.
Surface wound infections may be treated with creams or ointments that kill bacteria. However, if ‘cellulitis’, a deep skin infection, is present, oral or intravenous antibiotics will be needed. Even mild peripheral vascular disease (disease of the blood vessels outside the heart and brain) should be corrected in these patients to help their wounds heal.
The necessary duration of antibiotics typically ranges from 2-4 weeks. If the patient has osteomyelitis (bone infection), they may need at least 6 weeks of treatment. Hyperbaric oxygen therapy – a treatment that involves breathing pure oxygen in a pressurized room or tube – can prevent the need for amputations in patients with severe ulcers. Hyperbaric oxygen works through various mechanisms, such as increasing oxygen delivery to tissues lacking oxygen, killing bacteria, aiding blood vessel formation, accelerating the growth of collagen and fibroblasts (types of cells), and reducing swelling. Nine studies have shown that hyperbaric oxygen therapy helps these patients heal faster, prevents amputations, and improves oxygen measurements in the skin. Hyperbaric oxygen increases the likelihood of wound healing by ten times. A standard treatment course is 30 to 40 treatments.
Surgical removal of dead tissue or ‘debridement’ is a key treatment for many foot infections in people with diabetes. This surgery involves removing the infected bone. In some cases, removing a toe may be necessary. Before any debridement, it’s beneficial to consult a vascular surgeon, a specialist in treating blood vessel diseases, because some patients may benefit from a bypass operation of a blocked blood vessel.
What else can Diabetic Foot Infections be?
When dealing with certain medical conditions, it’s possible to experience symptoms like:
- Thrombophlebitis (inflammation of a vein caused by a blood clot)
- Phlegmasia cerulean dolens (a severe form of deep vein thrombosis)
- Compartment syndrome (a painful and dangerous condition caused by pressure buildup from internal bleeding or swelling of tissues)
- An acutely cold limb (a limb suddenly becoming very cold)
- Venous stasis ulcer (an open sore that develops on the lower leg due to poor blood circulation)
What to expect with Diabetic Foot Infections
The outcome for a person with diabetes who has a foot infection relies on several factors, including their blood circulation and nerve function in the foot. Various studies have pointed out that kidney failure and significant circulatory problems in the limbs are two risk factors that could lead to amputation.
Over the last 20 years, having a certain type of infection known as MRSA has also been recognized as a risk factor for the infection getting worse. If patients don’t manage their blood sugar levels properly, the results can be negative, sometimes leading to amputation.
Even after a surgical procedure known as a bypass, healing is not guaranteed. This procedure, which is done to restore normal blood flow to an obstructed artery, is demanding and often unsuccessful. One of the main reasons for this is the small size of the target artery involved in the procedure.
People who end up needing amputation of a limb also have a higher risk of serious heart problems and stroke. Overall, the quality of life for individuals with diabetes who develop a foot infection is often poor.
Possible Complications When Diagnosed with Diabetic Foot Infections
Osteomyelitis is a severe infection that affects the bone and can be a potential complication if not properly managed. If the infection proceeds, it could lead to a bone fracture which is a significant crack or break in the bone. Further complications can include sepsis, which is a life-threatening reaction to an infection that can spread throughout the body.
Another possible complication is gangrene. This is a condition where body tissues die due to lack of blood supply, often because of an underlying illness, injury, or infection.
Necrosis is similar to gangrene, it involves the death of cells or tissues due to injury, disease, or lack of blood supply. The most severe complication is amputation, which is the surgical removal of a body part that’s severely damaged or diseased.
Possible Complications:
- Osteomyelitis (bone infection)
- Bone fracture
- Sepsis (body-wide infection)
- Gangrene (tissue death due to lack of blood supply)
- Necrosis (cell death)
- Amputation (surgical removal of a body part)
